Fossil bony fish (Teleostei) from Oligocene-Miocene marine sediments on southern New Zealand

Rust, Seabourne, 1975-

Over twenty significant specimens of Late Oligocene- earliest Miocene bony fish (teleost) have been recovered from North Otago and South Canterbury, South Island, New Zealand. The fossils, studied herein, semi-complete skeletons, rather than isolated bone fragments or otoliths. Most of these fossils were prepared manually and using pneumatic tools. These fossils are described and identified as belonging to at least six families of acanthomorph fishes which have not previously been described formally from the New Zealand fossil record. Previously Davis (1888) and Chapman (1918, 1934) described some Cenozoic marine teleosts from New Zealand. Since then fish remains have occasionally been mentioned in the literature, mostly incidental to other works (see Fordyce, 1991). Since 1980, major advances in fossil teleost research in New Zealand have included comprehensive studies of otoliths (e.g Schwarzans, 1984), and the description of a few Cenozoic fresh water galaxiids (McDowall, 1976; McDowall & Pole, 1997) and Cretaceous marine fish (Wiffen, 1989). Some notable Cenozoic marine teleost skeletal specimens have been collected since the 1930's but were not recorded or studied in detail until this work. The Oligocene - Miocene fossil fish reported here come mainly from the Kokoamu Greensand and Otekaike Limestone, which represent the local Duntroonian and Waitakian Stages. These strata include the Globigerina euapertura and Globoquadrina dehiscens planktic foraminiferal zones of Jenkins (1971), equivalent to Late Miocene and earliest Miocene .. The limestone and greensand yield other fossils, including a rich invertebrate macrofauna, penguins, chondrichthyans and cetaceans (e. g. MacKinnon et al. 1993; Beu & Maxwell, 1990; Fordyce, 1991), and have been dated using foraminiferal biostratigraphy (e. g. Hornibrook et al., 1989). The accounts herein of the litho- and biostratigraphy of these units is based mainly on existing work, supplemented by my observations. The remains of a large and relatively complete bony fish (teleost) recovered from Oligocene limestone at Island Cliff, near Tokarahi, North Otago, are described. This fossil (OU 22268) probably represents a new genus of lampridiform related to the extant moonfish or opah (Lampris). OU 22268 is the only known specimen of this genus, and is the first fossil lampridiform recorded from the Southern Hemisphere. It is by far the largest fossil teleost found in New Zealand, and is one of the most complete. OU 22268 resembles Lampris having over 40 vertebrae and a Lampris-like caudal skeleton with a five hypurals, but differs in possessing a larger and more elongate body (estimated total length >4 m). A comparative study of the living southern moonfish Lampris immaculatus helped assess relationships of OU 22268. The specimen was also analysed using a cladistic framework based on Olney et al. (1993). The ii systematics and fossil record of the lampridiform fishes is reviewed, with particular attention on the deep-bodied ("bathysomus") forms: the Lamprididae and Veliferidae. Other Oligocene teleosts described herein are relatives of the swordfish (Xiphidae) and marlin (Istiophoridae ), including the now-extinct families Paleorhynchidae and Xiphiorhynchidae. These fossil billfish are mostly disarticulated vertebrae and caudal elements that cannot be identified beyond family level, although two specimens of the large paleorhynchid Pseudotetrapturus include significant skull material. One -4 m long Pseudotetrapturus specimen (OU 22396) was collected during this project from Haughs Quarry, Hakataramea, South Canterbury, and was prepared by the author. It has a distinctive long, narrow and sharply pointed lower jaw. The ventral' part of. the cranium of this specimen shows large orbits. A second smaller specimen (OU 22317) may represent a juvenile Pseudotetrapturus. All of the fossil billfish are described for the first time from New Zealand, and are among the first to be recorded from the .Southern Hemisphere. Relatives of the billfish, Acanthocybium and Gymnosarda-like "Spanish mackerals" of the family Scombridae are represented by two fossil.hypural plates from North Otago. Cod-like I (gadiform) fishes were also present during the Oligocene, with one disarticulated specimen described but not identifiable to family level. These finds hint at the diverseichthyofauna that existed in shelf waters around New Zealand during the mid-Cenozoic. The fossils are ·important in a global context as few south Pacific fossil fish skeletons are known from this interval. None of the fossils show structures that reveal distinctive particular lifestyles for the species involved, so the paleoecology of the fish is determined using taxonomic uniformitarianism - it is assumed they functioned in a similar way to their living counterparts. Thus most of the fossil fish identified so far· were pelagic predators. The billfish, presumably had thermal preferences like their living counterparts. Their presence as fossils in Otago and Canterbury supports the hypothesis of a relatively warm shallow sea covering much of New Zealand during the Oligocene.

ix, 148 leaves, 20 leaves of plates : ill. ; 30 cm.

2000Rust